ANS:B - viscous

Agitated film evaporators are particularly suitable for concentrating viscous liquids. Explanation:

• Agitated film evaporators are designed to handle liquids with challenging characteristics, such as viscosity and fouling tendencies.
• The agitation provided by mechanical agitators or rotating blades helps break up the liquid film on the heat transfer surface, preventing fouling and ensuring efficient heat transfer.
• Viscous liquids tend to form thick films on heat transfer surfaces, which can hinder heat transfer. The agitation in agitated film evaporators helps maintain turbulent flow and promote better mixing, enhancing heat transfer efficiency in viscous liquids.
• While agitated film evaporators may also be suitable for handling other challenging liquids, such as foaming or corrosive liquids, their design features are particularly well-suited for handling viscous fluids.
• Therefore, agitated film evaporators are commonly used in industries where the concentration of viscous liquids is required, such as in the food, pharmaceutical, and chemical industries.